Messages in this thread |  | | | Subject | Re: [PATCH] x86, efi: 1:1 pagetable mapping for virtual EFI calls | | From | Matt Fleming <> | | Date | Fri, 07 Sep 2012 09:02:11 +0100 |
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On Fri, 2012-09-07 at 08:40 +0100, Jan Beulich wrote: > >>> On 06.09.12 at 19:07, "H. Peter Anvin" <hpa@zytor.com> wrote: > > Anyone care to refresh my memory why we can't use the "global" > > 1:1+kernel map, possibly with some improvements (which would benefit the > > users of those maps too)? With that I mean initial_page_map on i386 and > > trampoline_pgd on x86-64... > > I don't think you want anything inserted in the low part of those > (kernel-only) page tables, not even transiently.
There are already things inserted into the low part of those page tables. In fact, the main purpose is to provide a 1:1 mapping for realmode code. See machine_real_restart().
I think there's definitely merit to the approach Peter outlined above. There's a variety of places in arch/x86 where a 1:1 mapping is needed. It would be good to have a single pagetable that provides this.
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